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## Resource: Introduction

## Article: Introduction

## Article Link: https://dev.wix.com/docs/api-reference/crm/members-contacts/members/member-management/custom-fields/custom-field-applications/introduction.md

## Article Content:

# About the Custom Field Applications API

The Custom Field Applications API allows you to decide which [custom fields](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-fields/introduction.md) apply to specific members. By default, newly created custom fields apply to all members on a Wix site. However, this API enables you to restrict fields to selected members based on:

- A list of IDs.
- Their member role.
- A badge they hold.
- Pricing plan they have purchased.

With the Custom Fields Applications API you can:

- [Create](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/create-custom-field-application.md) a custom field application.
- [Retrieve](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/get-custom-field-applications.md) custom field application details.
- Retrieve custom field applications for [members](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/get-members-custom-field-applications.md) and [roles](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/get-roles-custom-field-applications.md).
- [Delete](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/delete-custom-field-application.md) and [update](https://dev.wix.com/docs/rest/crm/members-contacts/members/custom-fields/custom-field-applications/update-custom-field-application.md) a custom field application.

## Before you begin

It’s important to note the following before starting to code:

- A site must have the [Wix Members Area](https://www.wix.com/app-market/web-solution/members-area) installed from the App Market.
- In a custom field application, `exclusions.items` override `applications.items`. For example, if you assign a "Favorite Animal" custom field to a specific member but exclude this field from the "Silver Plan" pricing plan, the member will not have access to the "Favorite Animal" field if they are part of the "Silver Plan."

## Terminology

- **Custom Field**: A user-defined field that extends the default member profile information.
- **System Field**: A Wix-defined field from the default member profile information.

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